1. Field of the Invention
The present invention relates to an image pickup element and an image pickup apparatus, in particular, an image pickup element capable of obtaining a plurality of parallax image signals, and an image pickup apparatus including the image pickup element.
2. Description of the Related Art
In the related art, there has been proposed an image pickup apparatus in which an exit pupil of a photographing lens is divided into a plurality of regions so that a plurality of parallax images corresponding to the pupil regions obtained by the division are photographed simultaneously.
U.S. Pat. No. 4,410,804 discloses an image pickup apparatus using a two-dimensional image pickup element in which one microlens and a plurality of divided photoelectric conversion portions are formed for one pixel. The divided photoelectric conversion portions are configured to receive light from different pupil subregions of the exit pupil of the photographing lens through one microlens to divide the pupil. Respective signals obtained by receiving the light by the divided photoelectric conversion portions generate a plurality of parallax images corresponding to the pupil subregions. Japanese Patent Application Laid-Open No. 2001-083407 discloses adding all signals, which are obtained by receiving light by divided photoelectric conversion portions in a pixel, to generate a picked-up image of a subject.
A plurality of photographed parallax images are equivalent to Light Field (LF) data, which is information on a space distribution and an angle distribution of light intensities. Stanford Tech Report CTSR 2005-02, 1 (2005) discloses a refocusing technology in which a synthetic image at a virtual imaging plane, which is different from an image pickup plane, is rendered by using obtained LF data to change a focus position of the picked-up image after photographing.
Japanese Patent Application Laid-Open No. 2008-299184 discloses an image pickup apparatus using an image pickup element. The image pickup element includes a shielding layer including aperture portions formed between a microlens and a light receiving surface of a photoelectric conversion portion of each pixel to shield light in most (a half or more) of the region excluding a part of the light receiving surface. Japanese Patent Application Laid-Open No. 2008-299184 discloses an image pickup element configured to decenter aperture portions of the shielding layer in a predetermined pattern for each pixel included in a set of pixels to receive light from different pupil subregions of the exit pupil of the photographing lens. In this manner, the exit pupil of the photographing lens is divided to photograph a plurality of parallax images corresponding to the pupil subregions obtained by the division. Such pixel configuration may be formed by utilizing a wiring layer to form the shielding layer including the aperture portions in a normal imaging pixel. It produces the image pickup element, which obtains the plurality of parallax images with a simple structure.